Almost every town/city is situated on either sides of a river – big or small. River provides mainly water for the inhabitants. In some rivers we find water in only some seasons. In others water flows all through the year. Such rivers are perennial in nature. River Seine in Paris, Thames in London, Tyne in New Castle, Ganga in Varanasi, Coovam in Chennai are good examples. In fact, human beings preferred to settle on the banks of these rivers. Most of our human civilization originated on either side of these great rivers. River water is not salty so it is suitable for drinking and irrigation. Some kind of fishes also lives in river water. Rivers do bring silt along and deposit on the river beds. River sand is in great demand nowadays for the huge construction industry. The origin of river water is rain or melting snow/ice from mountains. Generally rivers do not flow straight. They flow according to the slope and often take a zig zag direction touching various spots delivering water to this thirsty earth.
The flow of river water is checked by check dams built by men at various points so that they can tap the precious water for farming, industries and human needs. The topography of the land helps in establishing big or small dams. These dams discharge the impounded water whenever needed. The water in the river is partly used and the rest, unused ones reach the sea and become salty! As the water scarcity is mounting everywhere on earth, people try to impound it in dams and tanks preventing it to flow into the sea. Some big rivers are used for transportation. Small boats are used to go from one place to other carrying goods or crossing river. A cheap way of transport indeed! Swimming and bathing in river is a real joy for all. In festival seasons huge crowds go to river to bath and wash off their sins.
Rivers travel across States of Nations and also across Nations of the world.
Scarcity of water leads to larger disputes between States and Nations. Filing cases in courts leads to complications. If more water is available, then sharing becomes easy. At times, when water becomes limiting all kinds of problems arise. Each State or Nation fully utilize the water for their use and the rest is let out to others. This is quite normal. River water problems exist everywhere on earth. When flooding occurs, rivers overflow and water enters either side of the rivers and damage crops and human settlements. In order to cross the river, bridges are being constructed at various points. Road and rail bridges are generally constructed across rivers. Some of the bridges are really engineering marvels.
Thus rivers are essential for all living organisms. Some of the rivers are damaged by dumping trashes and industrial effluents. But in certain countries like UK and Singapore I witnessed clean rivers with clean water. So it is possible to have rivers of such standard everywhere on earth if human beings want.